(1) Field of the Invention
The present invention relates to a laser projection display device that displays an image by scanning source light of a semiconductor laser, etc. using a two-dimensional (2D) scanning mirror.
(2) Description of the Related Art
Recently, a small projector using a two-dimensional (2D) scanning mirror such as a micro electro mechanical systems (MEMS) mirror and a light source of a semiconductor laser has been put to practical use, and has been used as, for example, a head-up display for supporting driving of a vehicle. In such a laser projection display device, a desired image is projected onto a projection surface by modulating a laser source simultaneously with scanning a 2D scanning mirror in horizontal and vertical directions. Herein, a light modulating mechanism that modulates intensity of projection light according to ambient brightness has been proposed to improve visibility of a projection image.
For example, JP 2010-072365 A describes an on-board head-up display including a combiner that guides information to be displayed to a predetermined position, transmitted light quantity adjusting means that changes quantity of transmitted light of the combiner based on ambient brightness, and brightness detecting means that detects ambient brightness.
In addition, JP 2002-104017 A describes a light modulating mechanism of a head-up display including a screen formed by stacking at least a liquid crystal member and a light transmitting reflection member, and control means that applies a voltage to the liquid crystal member stacked in the screen according to a predetermined instruction signal and adjusts quantity of light penetrating the screen.